Structural investigations on the Nodal-Cripto binding: a theoretical and experimental approach.

Nodal, a member of the transforming growth factor-β superfamily, is a potent embryonic morphogen also implicated in tumor progression. Up to date structural information on the interaction of Nodal with its molecular partners are unknown. To deepen our understanding about mechanisms underlying both embryonic development and Nodal/Cripto-dependent tumor progression, we present here a molecular model of activin receptor-like kinase 4/Cripto/Nodal complex built by homology modeling as well as docking tests aimed at identifying potential binding epitopes.

Structural insights into the interaction between the Cripto CFC domain and the ALK4 receptor.

The protein Cripto is the founding member of the extra-cellular EGF-CFC growth factors, which are composed of two adjacent cysteine-rich domains: the EGF-like and the CFC. Members of the EGF-CFC family play key roles in embryonic development and are also implicated in tumourigenesis. Cripto is highly over-expressed in many tumours, while it is poorly detectable in normal tissues.

Abeta(25-35) and its C- and/or N-blocked derivatives: copper driven structural features and neurotoxicity.

The toxic properties of beta-amyloid protein, Abeta(1-42), the major component of senile plaques in Alzheimer's disease, depend on nucleation-dependent oligomerization and aggregation. In addition, Abeta(1-42) toxicity is favored by the presence of trace metals, which affect the secondary structure of the peptide. A peptide comprising 11 residues within Abeta(1-42) [Abeta(25-35)] aggregates and retains the neurotoxic activity of Abeta(1-42).

Solution structure of mouse Cripto CFC domain and its inactive variant Trp107Ala.

We report here for the first time the solution structures at pH 3 and pH 6 of the synthetic CFC domain of mouse Cripto and of the point mutated variant W107A that is unable to bind to the Alk4 Cripto receptor. NMR data confirm that the CFC domain has a C1-C4, C2-C6, C3-C5 disulfide pattern and show that structures are rather flexible and globally extended, with three noncanonical antiparallel strands. His104 and Trp107 side chains protrude from a protein edge and are strongly exposed to solvent, supporting previous evidence of direct involvement in receptor binding.

The chemical synthesis of the GstI protein by NCL on a X-Met site.

The small GstI protein (63 amino acids) of Rhizobium leguminosarum is the endogenous inhibitor of the glnII (glutamine synthetase II) gene expression. It has been suggested that GstI has a predominantly beta-structure and mediates the block of translation and stabilization of glnII mRNA through direct binding to its 5' untranslated region. Because of the unavailability of adequate amounts of purified recombinant protein, the mechanism as well as the protein tridimensional structure remain very poorly understood.

Chemical synthesis of mouse cripto CFC variants.

We report for the first time the chemical synthesis of refolded CFC domain of mouse Cripto (mCFC) and of two variants bearing mutations on residues W107 and H104 involved in Alk4 binding. The domains undergo spontaneous and quantitative refolding in about 4 h, yet with very different kinetics. Disulfide linkages have been assessed by enzyme digestion and mass spectrometry analysis of resulting fragments, and the first experimental studies on structural organization have been conducted by circular dichroism spectroscopy under different pH conditions.

A new ligand for immunoglobulin g subdomains by screening of a synthetic peptide library.

By screening a synthetic peptide library of general formula (NH(2)-Cys1-X2-X3-X4)(2)-Lys-Gly-OH, a disulfide-bridged cyclic peptide, where X2-X3-X4 is the tripeptide Phe-His-His, has been selected as a ligand for immunoglobulin G (IgG). The peptide, after a preliminary chromatographic characterization, has proved useful as a new affinity ligand for the purification of polyclonal as well as monoclonal antibodies from biological fluids, with recovery yields of up to 90% (90% purity). The ligand is able to bind antibody fragments containing both Fab and Fc from different antibody isotypes, a fact suggesting the presence of at least two different antibody-binding sites.